Evolution of ns pulsed laser induced shock wave on aluminum surface by numerical simulation

Abstract

Pulsed laser-induced shock wave (PLISW) is the key effect on the laser micro-and nano-structure processing. However, thus far, the effect of changing the laser parameters on the evolution of the PLISW is not clear. In this work, a two-dimensional numerical calculation model is established to analyze the PLISW based on the interaction between the ns laser and aluminum target. The results show that the laser parameters, such as energy density, spot size, and evolutionary time, can affect the evolution of the PLISW. The overpressure and wavefront velocity of the PLISW increase rapidly after ns laser processing. At a laser energy density of 3.4 J/cm2 at approximately 13 ns, the overpressure reaches the peak value of 110 MPa. When the time is approximately 70 ns, the velocity peak value appears, and afterward, it gradually attenuates. At laser energy density of 4.3 J/cm2, the peak value of the overpressure is instantaneously enhanced and reached 167 MPa. These results are consistent with the experimental results obtained by Porneala C in 2009. Furthermore, under fixed laser power, the shock wave becomes more uneven in the axial and radial directions as the laser spot increases. In the initial stage of the formation of the shock waves, the radial radius of the shock waves induced by a large laser spot is large. With the evolution of the shock wave, the shape of the wavefront gradually becomes consistent. For asymmetric double Gaussian laser spot, the shock wave effect is significantly amplified. Additionally, the superimposed influence of pressure waves leads to the decrease in the peak value of the overpressure, and the attenuation trend of the overpressure becomes slow.